Okay, but closures aren't Lisp-specific. Javascript and Lua have them, C# is about to get them, and the C++ standards board is considering them, plus probably dozens of other languages which I don't have experience with.

Closures can be used for OOP.. not that you'd want to, though.

Yes, the its the feature of closures that is important, and so much not the particular language that it's implemented in. (As Mark Jason Dominus said, "In another thirty years people will laugh at anyone who tries to invent a language without closures, just as they'll laugh now at anyone who tries to invent a language without recursion.")

A hash table in a closure can do a lot of things that OOP does with very little work-- but I wouldn't necessarily do things that way except for the fun of it. There are certainly much more interesting/subtle/powerful things that can be done with closures.